Disk files are information storage devices which utilize at least one rotatable disk with concentric data tracks containing the information, a transducer (or "head") for reading data from or writing data to the various tracks, and a head positioning actuator connected to the head for moving it to the desired track and maintaining it over the track centerline during read or write operations. The transducer is attached to a slider having an air bearing surface which is supported adjacent the data surface of the disk by a cushion of air generated by the rotating disk. The slider is attached on its back side (the side opposite the air bearing surface) to the suspension, and the suspension is attached to a support arm of the head positioning actuator.
The suspension provides dimensional stability between the slider and actuator arm, controlled flexibility in pitch and roll motion of the slider relative to its direction of motion on the rotating disk, and resistance to yaw motion. The suspension typically provides a load or force against the slider which is compensated by the force of the air bearing between the slider's air bearing surface and the disk surface. Thus, the slider is maintained in extremely close proximity to, but out of contact with, the data surface of the disk. The suspension typically comprises a load beam, which is mounted at one end to the actuator arm, and a flexure element which is attached to the other end of the load beam and supports the slider. The load beam provides the resilient spring action which biases the slider toward the surface of the disk, while the flexure provides flexibility for the slider as the slider rides on the cushion of air between the air bearing surface and the rotating disk. Such a suspension is described in U.S. Pat. No. 4,167,765, which is assigned to the same assignee as this application. An example of a conventional slider is described in U.S. Pat. No. 3,823,416, which is assigned to the same assignee as this application.
In the conventional slider-suspension assemblies, the slider is mechanically attached to the flexure of the suspension by epoxy bonding. The electrical connection between the transducer and the disk file read/write electronics is made by twisted wires which run the length of the suspension load beam and extend over the flexure and slider. The ends of the wires are soldered or ultrasonically bonded to the transducer leads on the slider. The fabrication of such a slider-suspension requires manual assembly and is thus time consuming and costly.
Another type of suspension is a composite or laminated structure comprising a base layer with patterned electrical leads formed thereon and an insulating cover layer, as described in IBM Technical Disclosure Bulletin, Vol. 22, No. 4 (Sept. 1979), pp. 1602-1603 and Japanese Kokai Nos. 53-74414 (Jul. 1, 1978) and 53-30310 Mar. 22, 1978). In the laminated suspension described in Japanese Kokai 53-74414, the slider is epoxy bonded to the laminated suspension and the transducer leads are soldered to the electrical leads formed on the suspension.
A disadvantage with conventional epoxy bonding of the slider to the suspension is that it is difficult to form the assembly such that the slider will have a predetermined pitch or roll relative to its direction of motion on the disk. Since the epoxy bonding can only result in a generally parallel relationship between the back side of the slider and the flexure of the suspension, the flexure must be formed or bent prior to bonding in order to give the slider a predetermined pitch or roll. Also, if it is desired to bond the slider to the suspension at a skew angle in order to optimize the angle between the slider's leading edge and the data track, some type of fixture is required to align the slider at the time the epoxy bond is formed.
An additional disadvantage with epoxy bonding is that because the epoxy is nonconductive, there is no consistent grounding path between the slider and the suspension. Thus in the event of static charge build-up on the slider the closest path for discharge is from the pole tips of the transducer to the disk surface. Static discharge through this path will destroy a thin film transducer.
Static charge build-up on the disk can also destroy a thin film transducer if the static discharge occurs from the disk to the pole tips of the transducer. This is because in conventional slider-suspension assemblies which have only one active thin film transducer on the slider, there is no grounding path from the pole tips of the inactive transducer.